I have checked kernel module for this adapter, it is there and the wifi firmware is also latest and up to date.Д«ut in /val/log/messages i can see the below error 'Dec 3 18:03:04 raspberrypi kernel: r8188eu: module is from the staging directory, the quality is unknown, you have been warned.' After configuring (I have copied all config details in subsequent section) necessary (what i feel) files also it is not working.Д®thernet port has lan cable plugged in and works fine (DHCP configured)Д«efore configuring wifi setting (in /etc/interfaces and /etc/wpa_supplicant/wpa_nf files), things went fine and my pi was accessible via lan ethernet interface, but once i plug in wifi USB adapter, after configuring /etc/interfaces and /etc/wpa_supplicant/wpa_nf files, the pi looses connection and i am not able to reach pi via its LAN interface.Д«ut if i takeout USB wifi Adapter the PI is accessible again.

I have leoxsys LEO-NANO150N (RTL8188EUS) wifi adapter and inserted into one of the USB port is Raspberry pi module. 'Linux Raspberry pi 4.1.13+ #826 PREEMPT Fri Nov 13 20:13: armv6l GNU/Linux' It is 'Raspberry Pi 1 model B+' and it has Rapbian installed on it OS Version: Installed OS is Rapbian Jessie (-raspbian-jessie.img)

Raspberry pi realtek rtl8188etv